Preparation of monohaloacetyl halides

ABSTRACT

A PROCESS FOR THE PREPARATION OF MONOHALOACYL HALIDES BY HALOGENATING KETENES IN THE PRESENCE OF AN ALKOXYALKYL ESTER.

"United States Patent US. Cl. 260-544 Y 1 Claim ABSTRACT OF THEDISCLOSURE A process for the preparation of monohaloacyl halides byhalogenating ketenes in the presence of an alkoxyalkyl ester.

This application is a continuation-in-part of copending application Ser.No. 185,402 filed Sept. 30, 1971, now abandoned.

This invention relates to the preparation of monohaloacyl halides by theliquid phase halogenation of ketenes. More particularly, this inventionrelates to the halogenation of ketenes in the presence of a solvent or areaction medium that inhibits or prevents the formation of polyhaloacylhalides and minimizes the formation of acyl halides. The term halogen asused herein includes chlorine, bromine, iodine and halogen halides suchas iodine monochloride, iodine monobromide, bromine monochloride and thelike.

The liquid phase halogenation of ketene is well known but the previouslyknown methods of conducting this reaction have resulted in the formationof monohaloacetyl halides contaminated with a considerable proportion ofpolyhaloacetyl halides. These earlier methods utilized such solvents aschlorinated benzenes, nitrobenzene, carbon tetrachloride, ethyl acetate,chloroacetyl chloride, acetyl chloride, 1,2 dichloroethane,acetonitrile, benzonitrile, nitromethane and various other solvents.Each of these solvents had a common shortcoming; that is, they allresulted in the formation of a considerable amount of dihaloacetylhalide, together with the desired product, monohaloacetyl halide. Insome of these solvents, the undesired trihaloacetyl halides were alsoformed. The dihalo deriva tives have no commercial utility and theirseparation from the monohalo derivative is expensive and time consuming.For example, dichloroacetyl chloride has a boiling point ofapproximately 107 C. whereas monochloroacetyl chloride has a boilingpoint of about 105 C. This proximity of the boiling points of these twocompounds renders their separation exceedingly difficult and also addsan expensive and uneconomical step to the halogenation process whenutilized in the previously known solvents.

The monohaloacetyl halides produced by the process of this invention arevaluable intermediates in the production of herbicidalalpha-haloacetoanilides and other products. By contrast, thecorresponding diand trihaloacetyl halides have no commercialsignificance. In other words, they are present merely as diluents whichdetract from the ellicacy of the commercially valuable monohaloacetylhalides. The severity of the problem is evidenced by the fact that allcommercially available chloroacetyl chloride is contaminated withappreciable amounts of dichloroacetyl chloride, and in some instancesthe dichloroacetyl chloride content is as great as six percent.

In accordance with the present invention, the disadvantages of the priorart solvents are overcome by the halogenation of a ketene in thepresence of an alkoxyalkyl ester of the formula wherein R and R are eachalkyl having a maximum of 5 carbon atoms, and R is alkylene having amaximum of 5 carbon atoms with the total number of carbon atoms in R, Rand R being at least 3 and not greater than 10.

The process of the present invention encompasses the halogenation ofketene, i.e. CH =C=0, as well as substituted ketenes, such as methylketene, dimethyl ketene, ethyl ketene, diethyl ketene, phenyl ketene,diphenyl ketene and the like.

While 2-methoxyethyl acetate is generally preferred, other alkoxyalkylesters can be used alone or in any combination for the purposes of thisinvention. Suitable esters include, for example, 2-methoxyethyl acetate,Z-ethoxyethyl acetate, 2-propoxyethyl acetate, 2-butoxyethyl acetate,2-pentoxyethyl acetate, methoxymethyl acetate, ethoxymethyl acetate,propoxymethyl acetate, butoxymethyl acetate, pentoxymethyl acetate,methoxypropyl acetate, ethoxypropyl acetate, propoxypropyl acetate,butoxypropyl acetate, pentoxypro pyl acetate, methoxybutyl acetate,ethoxybutyl acetate, propoxy-butyl acetate, butoxybutyl acetate,pentoxybutyl acetate, methoxypentyl acetate, ethoxypentyl acetate,propoxypentyl acetate, butoxypentyl acetate, and the correspondingpropionates, butyrates and valerates having a maximum of 10 carbon atomsin the alkyl and alkylene groups.

In carrying out the process of the present invention, a ketene and thehalogen are introduced into the solvent medium where they react to form.a monohaloacyl halide which is separated from the reaction medium byconventional means such as distillation, preferably at reduced pressure.The process is amenable to either continuous or to batch type operation.The operating conditions under which the reaction is conducted are notcritical but it is preferred to maintain them within specified limits tomaximize the yield of the monohaloacyl halides. In essence, it is onlynecessary that the ester is liquid under reaction conditions. Because ofpractical considerations, however, the reaction is normally conductedwithin the approximate temperature range of -50 C. to 150 C. at apressure from about 50 mm. Hg to about 2 atmospheres. In most instances,however, it is preferred to operate at a temperature between about 0 C.and about 110 C. at a pressure between about mm. and about 760 mm. Thereaction of the halogen and the ketene progresses to form monohaloacylhalides while minimizing formation of the corresponding polyhalocompound regardless of the mole ratio of the reactants. The advantagesof the present invention are more fully realized, however, when the moleratio of halogen to ketene is maintained between about 08:1 and about2:1 and optimum results are obtained with mole ratios of halogen toketene between about 1:1 and about 13:1. The presence of an alkoxyethylester of the present invention in the reaction medium minimizes theformation of acyl halides and substantially reduces the formation ofdihaloacyl halides and other polyhalogenated by-products.

In accordance with the present invention, the alkoxyalkyl ester canconstitute substantially all or only a minor portion of the reactionmedium. The benefits of the is high, i.e. about 85-9O percent and theamount of di haloacyl halide produced is minimized, i.e. a yield of lessthan about percent.

TABLE I Example number 2 3 4 5 6 Solvent 2-pentoxyethyl 3-butoxypropy14-meth0xybutyl Z-methoxyethyl 3-methoxypropy1 etate. acetate. acetate.acetate. acetate.

125- 760. mperature C.) 30,

Ketene Phenyl ketene. Halogen Chlorine Chlorine Chlorine. Solvent amount(parts)- 250 200..- 170. Hologen Amount (parts) 170. 127. 60. KeteneAmount (parts)- 100 75 150... 60 100. Haloaeyl Halide ChloroacetylChloroacetyl chloroacetyl Bromoacctyl 2-chloro-2-phcnylacety1 chloride.chloride. chloride. bromide. chloride. Dihaloacyl Halide DichloroacetylDichloroacetyl Dichloroacetyl Dibromoacetyl2,2-diehloro-2-phenylchloride. chloride. chloride. bromide. acetylchloride.

present invention are most pronounced when the solvent weight ratio ishigh but substantial benefits are realized even when the ester ispresent in relatively small amounts. The weight ratio of the alkoxyalkylester to the sum of the ester and the product, i.e., the solvent weightratio, can vary from about 0.05:1 to about 0.99:1. In fact, during thenormal course of a batch reaction, the solvent weight ratio diminisheswith the formation of the product which becomes mixed with the esterforming the reaction medium. In the practice of the continuous process,the solvent weight ratio can be maintained constant or varied to desiredlevels.

The invention Will be more clearly understood from the followingdetailed description of specific examples thereof. In these examples andthroughout the specification all proportions are expressed in parts byweight unless otherwise indicated.

\ EXAMPLE 1 About 168 parts (Solvent Amount) of Z-methoxyethyl acetate(Solvent) were charged into a suitable reaction vessel provided withagitation means, a gas outlet, temperature recording means and two gasspargers below the level of the Z-methoxyethyl acetate. With continuousagitation at atmospheric pressure (Pressure) with the reaction mediummaintained at a temperature of approximately 24 C. (Temperature) ketene(Ketene) and chlorine (Halogen) were introduced through separatespargers at constant and substantially equimolar rates. After about 3hours, the addition of the reactants was terminated. About 192 parts(Halogen Amount) chlorine and about 98 parts (Ketene Amount) ketene hadbeen added during the course of the reaction. At the termination of thereaction, the ratio of the solvent to the sum of the solvent and productwas about 0.46:1. The reaction mixture contained 2-methoxyethyl acetate,chloroacetyl chloride (Haloacyl Halide) and small amounts of acetylchloride and dichloroacetyl chloride (Dihaloacyl Halide). Upondistillation to recover the solvent and to separate the chloroacetylchloride, the mole percent yield of chloroacetyl chloride was determinedto be on the order of 89%. About 2.7% dichloroacetyl chloride and about8% acetyl chloride were also formed.

Although in this example the reaction mass was agitated, agitation isnot necessary in the halogenation process of this invention. Whenbromine is the halogen, it is preferred to agitate the reaction mass butgood results are also obtained without agitation.

Following the general procedure of Example 1 but with conditions andmaterials changed as noted in Table I the indicated products areobtained. The line titles of Table I are shown in parenthesis in thedescription of Example 1 where appropriate.

In Examples 2 through 6 the yield of haloacyl halide In order toillustrate the advantages of the solvents of the present invention, theprocedure of the foregoing Example 1 was substantially duplicated usingother solvents. The percent yields thus obtained, together with theresults of Example 1 are tabulated below in Table II.

ing previously known solvents, it is self-evident that utilization ofthe solvents of the present invention substantially suppresses theformation of dichloroacetyl chloride. It is also evident that thissolvent system minimizes the formation of acetyl chloride anddichloroacetyl chloride without undergoing extensive degradation orreaction itself which would lead to additional contaminants andchlorinated impurities in the chloroacetyl chloride produced. The highsolvent recovery indicates that this solvent is intrinsically eifectivein this reaction.

The beneficial results of the present invention are obtained in likemanner with other solvents under consideration as well as with bromineand the other aforementioned halogenating agents. Bromine can beintroduced into the system as the liquid, combined with the ester insolution, or in the gaseous state below the surface of the reactionmass. In most instances it is preferred to conduct brominations inaccordance with this invention by using a solution of .bromine in theester solvent. When iodine monochloride is used as the halogenatingagent, it can be charged into the reactor by dissolving it in the estersolvent and then adding the resulting solution to the system.

Although the invention has been described with respect to specificmodifications, the details thereof are not to be construed aslimitations except to the extent indicated in the following claim.

We claim:

1. A process for the preparation of chloroacetyl chloride whichcomprises reacting ketene and chlorine in the presence of Z-methoxyethylacetate.

References Cited UNITED STATES PATENTS 2,862,964 12/1958 Lacey 260-544 YLORRAINE A. WEINBERGER, Primary Examiner R. D. KELLY, Assistant Examiner

